mounting a persistent overlay

[James Heather]

Can anyone tell me how to mount the squashfs / persistent overlay on a
live USB stick, without booting it up?

Context: I gave someone a live USB stick with something
in /etc/rc.d/rc.local to log some diagnostics when he booted it up on a
machine in China. Now I want to get the logs off the USB stick, but I am
just realising in my amateurish way that when I boot it up I will
overwrite the logs... Such is the problem with operating under time
pressure...

James

[Keith Roberts]

On a running Linux box, you should be able to plug the USB 
stick into a USB port, and mount the squashfs filesytem the 
same way that you can mount an ISO image.

Once you have mounted the squashfs image, copy what you want 
to another directory on the running machine.

Just Google for 'squashfs mount'

HTH

Keith Roberts

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On Sun, 28 Mar 2010, James Heather wrote:
> To: [e-mail]
> From: James Heather 
> Subject: [Fedora-livecd-list] mounting a persistent overlay
>
> Can anyone tell me how to mount the squashfs / persistent overlay on a
> live USB stick, without booting it up?
>
> Context: I gave someone a live USB stick with something
> in /etc/rc.d/rc.local to log some diagnostics when he booted it up on a
> machine in China. Now I want to get the logs off the USB stick, but I am
> just realising in my amateurish way that when I boot it up I will
> overwrite the logs... Such is the problem with operating under time
> pressure...
>
> James

[James Heather]

> On a running Linux box, you should be able to plug the USB 
> stick into a USB port, and mount the squashfs filesytem the 
> same way that you can mount an ISO image.

Thanks--yes--it's no problem mounting the squashfs.

The tricky part is how to mount the persistent overlay. After all,
that's where the additional files have been written...

James

[Xander Pirdy]

> The tricky part is how to mount the persistent overlay. After all, that's
> where the additional files have been written...

The way that I understand it is that in short, you can't, since the
persistent overlay is a copy on write table, that only really works by
marking changed blocks from what it overlays. Hence the size limit, the
corruption when it becomes full and the uselessness unless you boot into
that system. If I am wrong I would be glad to be corrected, because until
these issues get fixed I am sticking with live distributions that use
debian-live, which uses aufs, which doesn't corrupt is unlimited in size and
can be mounted out of context. But these features won't come to fedora until
a union-mount file system makes it into the mainline kernel (or so I have
heard).
Good Luck,
Alexander
> James
>
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Thanks--yes--it's no problem mounting the squashfs.